Project description:Comparison of gene expression between the virulent Rickettsia rickettsii R strain and avirulent Rickettsia rickettsii Iowa. Keywords: virulent vs avirulent
Project description:Comparison of gene expression between the virulent Rickettsia rickettsii R strain and avirulent Rickettsia rickettsii Iowa. Keywords: virulent vs avirulent Virulent Rickettsia rickettsii R strain in triplicate was compared to avirulent Rickettsia rickettsii Iowa in triplicate
Project description:Gram-negative bacteria in the order Rickettsiales are obligate intracellular parasites that cause human diseases such typhus and spotted fever. They have evolved a dependence on essential nutrients and metabolites from the host cell as a consequence of extensive genome streamlining. However, it remains largely unknown which nutrients they require and whether their metabolic dependency can be exploited therapeutically. Here, we describe a genetic rewiring of bacterial isoprenoid biosynthetic pathways in the Rickettsiales that has resulted from reductive genome evolution. We further investigated whether the spotted fever group Rickettsia species Rickettsia parkeri scavenges isoprenoid precursors directly from the host. Using targeted mass spectrometry in uninfected and infected cells, we found decreases in host isoprenoid products and concomitant increases in bacterial isoprenoid metabolites. Additionally, we report that bacterial growth is prohibited by inhibition of the host isoprenoid pathway with the statins class of drugs. We show that growth inhibition correlates with changes in bacterial size and shape that mimic those caused by antibiotics that inhibit peptidoglycan biosynthesis, suggesting statins inhibit cell wall synthesis. Altogether, our results describe an Achilles' heel of obligate intracellular pathogens that can be exploited with host-targeted therapeutics that interfere with metabolic pathways required for bacterial growth.
Project description:Rickettsia spp. are obligate intracellular bacterial pathogens that have evolved a variety of strategies to exploit their host cell niche. However, the bacterial factors that contribute to this intracellular lifestyle are poorly understood. Here, we show that the conserved ankyrin repeat protein RARP-1 supports Rickettsia parkeri infection. Specifically, RARP-1 promotes efficient host cell entry and growth within the host cytoplasm, but is not necessary for cell-to-cell spread or evasion of host autophagy. We further demonstrate that RARP-1 is not secreted into the host cytoplasm by R. parkeri. Instead, RARP-1 resides in the periplasm, and we identify several binding partners that are predicted to work in concert with RARP-1 during infection. Altogether, our data reveal that RARP-1 plays a critical role in the rickettsial life cycle.
Project description:Rickettsia parkeri, a recently recognized pathogen of human, is one of several Rickettsia spp. in the United States that causes a spotted fever rickettsiosis. To gain insights into its biology and pathogenesis, we applied the proteomics approach to establish a two-dimensional gel proteome reference map and combined this technique with cell surface biotinylation to identify surface-exposed proteins of a low-passage isolate of R. parkeri obtained from a patient. We identified 91 proteins by matrix-assisted laser desorption ionization-tandem time of flight mass spectrometry. Of these, 28 were characterized as surface proteins, including virulence-related proteins (e.g., outer membrane protein A [OmpA], OmpB, beta-peptide, and RickA). Two-dimensional immunoblotting with serum from the R. parkeri-infected index patient was utilized to identify the immunoreactive proteins as potential targets for diagnosis and vaccine development. In addition to the known rickettsial antigens, OmpA and OmpB, we identified translation initiation factor 2, cell division protein FtsZ, and cysteinyl-tRNA synthetase as immunoreactive proteins. The proteome map with corresponding cell surface protein analysis and antigen detection will facilitate a better understanding of the mechanisms of rickettsial pathogenesis.